Mechanism to make a heat sink in contact with a pluggable transceiver, a pluggable optical transceiver and a cage assembly providing the same

ABSTRACT

An inventive heat-dissipating mechanism between the pluggable optical transceiver and the heat sink with the thermo-conducting sheet is disclosed. One of the optical transceiver and the heat sink is adhered with the thermo-conducting sheet. The heat sink is assembled with the cage so as to be movable in vertical as causing the downward force. The optical transceiver provides a projection in the surface to be come in contact with the heat sink, while, the heat sink provides a rail with a pocket. When the transceiver is inserted into the cage, the projection first runs on the rail to lift the heat sink upward; subsequently, is fallen within the packet to adhere the thermo-conducting sheet to the transceiver.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. provisional application No. 60/996,924, filed Dec. 11, 2007, and claims priority from Japanese application, JP2007-329668, filed on Dec. 21, 2007, which are incorporated herein by reference in their entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a mechanism to dissipate heat from a pluggable optical transceiver, in particular, the invention relates to a structure of a heat sink provided in a cage to receive the pluggable optical transceiver.

2. Related Prior Art

An optical transceiver, which transmits and receives optical signals through an optical connector engaged therewith by optically active devices of a light-emitting device and a light-receiving device each made of semiconductor materials, generally includes a body that installs a plurality of electronic components, electronic circuits and circuit boards; and an optical receptacle that receives the optical connector. One type of optical transceivers is called as a hot-pluggable optical transceiver, in which the transceiver is inserted into or extracted from a cage provided on a host board to engage an electrical plug of the transceiver with an optical connector prepared in the deep end of the cage without turning off the power of the host system.

FIG. 6 schematically illustrates one type of the pluggable transceiver, what is called as the XFP. FIG. 6 illustrates a state where the XFP transceiver 3 is going to be installed on the host board. A Japanese Patent Application published as JP2007-156461A has disclosed such XFP transceiver 3. As illustrated in FIG. 6, on the host board 1 is provided with the metal cage 2 so as to expose the front end of the cage 2 with an opening 2 a from the bezel 1 a of the host system 1. The XFP transceiver 3 is inserted into or extracted from the opening 2 a. In the rear end of the transceiver 3 is formed with an electrical plug 4. The transceiver 3 may electrically communicate with the host system 1 by engaging this plug 4 with an optical connector, not shown in the figure, provided in the deep end of the cage 2.

On the top of the cage 2 is provided with a heat sink 6 to dissipate heat from the transceiver 3. The clip 7 bounds the heat sink with the cage 2. The roughness of the top surface of the transceiver 3 and that of the bottom surface of the heat sink 6, that is, the surfaces to be adhered to each other, affects the heat-dissipating efficiency.

Recent transmission speed in the optical communication system exceeds 10 Gbps and reaches 100 Gbps, which inevitably accompanies with the larger power consumption in the electronic and optical devices. An effective heat-dissipating mechanism is always required. It is inevitable to obtain the efficient heat conduction between solids, such as the contact between the housing of the transceiver and the heat sink of the cage, to widen a contact area and to make the surfaces to be contacted smooth as possible. However, the process to obtain such smooth surfaces is cost-ineffective and the outer dimensions of the transceiver do not permit the widened area.

Another method to secure the effective thermal contact between metals has been known, in which a viscous paste or a resin sheet with less hardness is put between the surfaces. Although the resin is inherently inferior in the thermal conductivity, it is applicable as a thermo-conducting sheet by merging metals or ceramics with good thermal conductivity in a shape of the powder and by thinning the thickness thereof as possible. Such a member, hereafter denoted as a thermo-conducting sheet, is applicable as a gap-filler put between two members rigidly fixed with respect to each other by removing air gaps and equivalently expands the contact area; accordingly, it secures the efficient heat transmission between members. However, it is insufficient for the heat transmission only to make it, the thermo-conducting sheet, in contact to each other; the control of an adequate pressure applied to the members and the thermal conductivity of the thermo-conducting sheet are necessary.

In a conventional pluggable optical transceiver, the heat-dissipation has been performed only by the physical contact between the housing of the transceiver and the heat sink without any thermo-conducting sheet. In another case where the heat generation in the transceiver is comparably less, the housing of the transceiver itself may perform the heat-dissipating function without coming in contact with the heat sink. However, recent pluggable optical transceivers have generated heat more and more as the transmission speed and the transmission distance increases, which inevitably requests the heat sink and the effective heat-dissipating path from the transceiver to the heat sink.

The pluggable optical transceiver, as its name indicates, is inserted into or extracted from the cage. Thus, the arrangement for the thermal contact between the housing of the transceiver and the heat sink is necessary not to obstruct the insertion or extraction of the transceiver. When the transceiver is inserted into the cage, the heat sink provided in the cage must be untouched to the housing until the transceiver is set in the regular position to secure the smooth insertion. The present invention is to provide such a mechanism between the housing of the transceiver and the heat sink.

SUMMARY OF THE INVENTION

One aspect of the present invention relates to a mechanism to dissipate heat from a pluggable optical transceiver set in a cage to a heat sink assembled with the cage through a thermo-conducting sheet put between the optical transceiver and the heat sink. The mechanism includes at lest a projection in a rear end of the optical transceiver, at least a rail with a pocket provided in the heat sink, and a mechanism provided in the cage and the heat sink to cause the downward force to the heat sink. In the present mechanism, the projection first lifts the heat sink upward withstanding the downward force by running on the rail when the transceiver is inserted into the cage. The projection finally falls within the pocket to adhere to thermo-conducting sheet to the optical transceiver when the optical transceiver is set in a final position within the cage.

The mechanism of the invention enables the thermo-conducting sheet to be apart from the surface of the transceiver to be come in contact with the heat sink until the optical transceiver is set in the final position, which may escape the thermo-conducting sheet from scraping with the transceiver and being peeled off. Moreover, the downward force caused in the heat sink becomes active at the final position of the transceiver; the effective heat-dissipating path may be secured from the optical transceiver to the heat sink.

Another aspect of the present invention relates to a pluggable optical transceiver to be set in a cage providing a heat sink to dissipate heat from the optical transceiver through a thermo-conducting sheet. The heat sink is applied with a downward force from the cage when the cage is free from the transceiver and provides a first rail with a first pocket and a second rail with a second pocket. The optical transceiver of the invention includes a first projection in a surface to come in contact with the thermo-conducting sheet and a second projection in the surface. The second projection is not over lapped with the first projection in a direction along which the optical transceiver is inserted into the cage. The first projection first runs on the first rail of the heat sink to lift the heat sink upward when the transceiver is inserted into the cage. The first projection is set within the first pocket and the second projection is set within the second pocket such that the heat sink is adhered to the surface of the transceiver with putting the thermo-conducting sheet therebetween when the optical transceiver is set in a regular position within the cage.

Third aspect of the present invention relates to a cage assembly for a pluggable optical transceiver. The cage assembly includes a cage and a heat sink. The cage provides a window in a top thereof and an elastic member to causing a downward force to the heat sink. The heat sink provided with a thermo-conducting sheet and exposes from the window of the cage. The heat sink is movable within the window in vertical, while, substantially immovable in horizontal. The heat sink also provides a rail with a pocket in a surface where the thermo-conducting sheet is adhered thereto. In the present cage assembly, the rail is run on with a projection provided in the optical transceiver to lift the heat sink upward withstanding the downward force when the optical transceiver is inserted into the cage. The pocket receives the projection to adhere the thermo-conducting sheet to the optical transceiver when the transceiver is set in the regular position within the cage.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1A is a perspective view schematically showing a heat-dissipating mechanism between the heat sink and the optical transceiver, and FIG. 1B is a cross section to show the motion of the transceiver and the heat sink according to an embodiment of the invention;

FIGS. 2A and 2B schematically show a side and plan views of the optical transceiver, while, FIGS. 2C and 2D show a plan and side views of the heat sink according to an embodiment of the invention;

FIGS. 3A to 3E show positional relations between the transceiver and the heat sink when the transceiver is set in the cage;

FIGS. 4A to 4C illustrate a structure of the heat sink and the cage to support the heat sink movable in vertical and immovable in horizontal;

FIG. 5A schematically illustrates a structure of the cage to cause the downward force to the heat sink, and FIG. 5B magnifies the structure shown in FIG. 5A; and

FIG. 6 illustrates a pluggable transceiver and a cage assembled with a heat sink by a conventional structure.

DESCRIPTION OF PREFERRED EMBODIMENTS

Next, preferred embodiments according to the present invention will be described in detail as referring to drawings. FIG. 1A is a perspective view that schematically illustrate the heat-dissipating mechanism according to an embodiment of the invention, and FIG. 1B is a cross section of the heat-dissipating mechanism.

The fundamental structure of the present heat-dissipating mechanism is similar to those appeared in the conventional mechanism such as those shown in FIG. 6. Referring to FIG. 1A, the host system 10 provides the host board 11 where the metal cage 12 is prepared thereon and the pluggable optical transceiver 13 is inserted into or extracted from the cage 12. In the front end of the cage 12 is provided with the opening 12 a that exposes from the bezel 11 a to receiver the transceiver 13.

The cage 12 has the box shape with the aperture 12 c in the top 12 b thereof to exposes the heat sink 15. The heat sink 15 assembled with the cage 12 such that the heat sink 15 is movable in up and down. The cross section of the side rib 16 controls the up and down motion of the heat sink 15 cooperating with tabs 17 formed in the side 12 d of the cage 12.

The optical transceiver 13 has the metal housing 14. When the transceiver 13 is set within the cage 12, the top 14 a of the housing 14 comes in thermally contact with the heat sink 15. FIG. 1B also illustrates the electrical plug 24 in the rear end of the transceiver 13. This plug 24 is to be mated with the connector 22 prepared in the deep end of the cage 12 to secure the communication, such as supply of the electric power from the host system to the transceiver 13 and the transmission of electrical signals between the transceiver 13 and the host system.

FIG. 1B illustrates the thermo-conducting sheet 18 between the bottom 15 a of the heat sink 15 and the top 14 a of the housing 14 to secure the heat conducting path from the transceiver 12 to the heat sink 15. In FIG. 1B, the heat sink 15 provides the thermo-conducting sheet 18. In order not to deteriorate the effective thermal transmission from the housing 14 to the heat sink 15, the thermo-conducting sheet 18 is necessary to be adhered to both the top 14 a of the housing 14 and the bottom 15 a of the heat sink 15. The thermo-conducting sheet 18 may be made of softened material with good thermal conductivity.

Specifically, the thermo-conducting sheet 18 may be made of resin such as silicone rubber, or may be made of hybridized material of organic and inorganic material containing, as a thermal conductive filler, metal powder of copper, aluminum, silver or stainless steel; or minute particles of oxide metal such as of aluminum oxide, titanium oxide or silicon oxide, nitride metal such as boron nitride, aluminum nitride, or chromium nitride; or other carbonized metal. The thickness of the thermo-conducting sheet 18 is preferably from 0.3 to 1.0 mm. Such a thermo-conducting sheet is easily available in the market.

The optical transceiver 13, as already described, is a type of the pluggable transceiver able to be inserted into and extracted from the cage 12. The transceiver 13 is necessary not to graze or not to peel the thermo-conducting sheet 18 by the insertion or the extraction. The transceiver 14 according to the present invention provides the projection 19 in both sides of the top 14 a of the housing 14, while, the heat sink 15 provides the rail 20 in both sides of the bottom 15 a thereof that receives the projection 19. Both the projection 19 and the rail 20 are formed in respective surfaces so as to escape the thermo-conducting sheet 18.

When the transceiver 13 is inserted into the cage, the projection 19 lifts up the heat sink 15, resisting the downward force for the heat sink 15 applied by the elastic tab 16, by abutting against the bottom 15 a of the heat sink 15 in the insertion of the transceiver 13. That is, the thermo-conducting sheet 18 may be apart from the top 14 a of the housing 14 without being grazed until the transceiver 13 is set in the final position in the cage 12.

At the final portion of the transceiver 13 in the cage 12, the rail 20 receives the projection 19, at which the heat sink 12 is pressed downward by the elastic force due to the side tab 17 to a position denoted by the chain line in FIG. 1B. Thus, the bottom 15 a of the heat sink 15 is pressed against the top 14 a of the housing through the thermo-conducting sheet 18. The mechanism described above may establish the effective heat-dissipating path from the transceiver 13 to the heat sink 15 without scraping or peeling the thermo-conducting sheet between the housing 14 and the heat sink 15.

FIGS. 2A to 2D exemplarily illustrate the projection 19 on the top 14 a of the housing 14 and the rail 20 in the bottom 15 a of the heat sink 15, respectively. FIGS. 2A and 2B are side and top views of the housing 14, while, FIGS. 2C and 2D are bottom and side views of the heat sink 15. The top 14 a of the housing 14 provides two types of projections, 19 a and 19 b, each accompanies with front and rear slopes 19 c. A distance between rear projections 19 a is narrower than a distance between front projections 19 b. That is, the rear projection 19 a is formed inwardly with respect to the front projection 19 b such that two projections, 19 a and 19 b, are not overlapped along the longitudinal direction of the transceiver. Moreover, because respective projections, 19 a and 19 b, provides the slope in both longitudinal sides to facilitate the mating with the rails, 20 a and 20 b, in the heat sink 15.

While the rail 20 in both sides of the heat sink 15 provides two tracks, 20 a and 20 b, each traced by the projection, 19 a or 19 b, in the housing 14. Here, only a center portion of the bottom 15 a of the heat sink 15 is adhered with the thermo-conducting sheet 18, and both side walls of the transceiver 13 provides the side rib 16. The first rail 20 a, namely the inner rail, receives the first projection 19 a, namely the rear projection, of the housing 14, while, the second rail 20 b, namely the outer rail, set outside to the first rail 20 a receives the second projection 19 b, namely the front projection. In the rear end of the first rail 20 a is formed with the pocket 20 d where the first projection 19 a is set therein, while, the rear end of the second rail 20 b provides the second pocket 20 e where the second projection 19 b is set therein. The ends of respective rails, 20 a and 20 b, are formed in slope 20 c to facilitate the slide of the projection, 19 a or 19 b, thereon.

FIGS. 3A to 3E schematically illustrate the mating mechanism between the projections, 19 a and 19 b, and the rails, 20 a and 20 b. When the transceiver 13 is free from the cage 12, the heat sink 15 is pressed downward by the elastic tab 17 of the cage 12; accordingly, it is necessary to lift the heat sink upward withstanding this downward force of the tab 17 when the transceiver 13 is to be inserted into the cage 12.

At the initial position of the transceiver 13 in the cage 12 shown in FIG. 3A, the first projection 19 a slides on the slope 20 c in the front end of the first rail 20 a and slips thereunder, that is, the first projection 19 a abuts against the bottom 15 a of the heat sink 15 to lift the front side thereof upward. Because the front end of the heat sink 15 is lifted upward, the insertion of the transceiver 13 into the cage 12 may be facilitated.

Subsequent to the initial position shown in FIG. 3A, the transceiver is further pushed into the cage until the first projection 19 a is in a midway of the cage 12 as shown in FIG. 3B, the other projection 19 b, the front projection, also comes in contact with the bottom 15 a of the heat sink 15, which makes the heat sink 15 in substantially horizontal.

FIG. 3C illustrates a status where the transceiver 12 is inserted to a position just before the final one where two projections, 19 a and 19 b, still come in contact with the respective rails, 20 a and 20 b, not set within the pockets, 20 d and 20 e. Slightly pushing the transceiver 13 from the position shown in FIG. 3C into the cage 12, only the first projection 19 a is set within the first pocket 20 d of the first rail 20 a, while, the other projection 19 b is still left on the second track 20 b, which leans the heat sink 15, that is, the front end of the heat sink 15 is again lifted up withstanding the downward force due to the elastic tab 17.

At the final position of the transceiver 13 in the cage, the second projection 19 b also falls into the second pocket 20 e, which the thermo-conducting sheet 18 between the housing 14 and the heat sink 15 is pressed by the downward force of the heat sink 15 by the elastic tab 17. When the transceiver 13 is extracted from the cage 12, the mechanism described above may also operate to the heat sink 15.

That is, the second projection 19 b first rides on the second rail to lift the front end of the heat sink 15 upward withstanding the downward force due to the tab 17 as shown in FIG. 3D. Next, the first projection 19 a also rides on the first rail 20 a in addition to the second projection 19 b, which levels the heat sink 15 as shown in FIG. 3C. Finally, only the first projection 19 a is left in a state to come in contact with the heat sink 15.

Thus, according to the embodiment described above, the transceiver 14 may be inserted into or extracted from the cage 12 without touching the top 14 a of the housing 14 to the thermo-conducting sheet until the transceiver 13 is set in the final portion where the plug 24 mates with the connector 22. The thermo-conducting sheet may be escaped from the grazing or peeling by the transceiver 13. Similarly, when the transceiver 13 is extracted from the cage 12, the mechanism according to the embodiment above firstly separates the thermo-conducting sheet 18 from the housing 14, and secondly moves the transceiver 12 from the cage 13.

FIGS. 4A to 4C, and FIGS. 5A and 5B explain an arrangement to assemble the heat sink 15 with the cage 12 as enabling to cause the downward force to the heat sink 15. FIGS. 4A to 4C are cross sections taken along the longitudinal direction.

As already explained, the heat sink 15 is assembled with the cage 12 such that the top of the heat sink with a plurality of fins exposes from the aperture 12 c of the cage so as to be slightly movable in vertical and substantially immovable in horizontal. The front and rear edges of the aperture 12 c are bent downward and a tip of the bent portion extends inside of the aperture 12 c to form a tip tab 12 e. While, the bottom corners of the front end rear ends of the heat sink 15 provide a step hooked on the tip tab 12 e. When the cage 12 is free from the transceiver 15, the heat sink 15 receives the downward force by the tab 17 in the side of the cage; this downward force may be compensated by this tip tab 12 e. When the cage 12 receives the transceiver 15, the heat sink 15 is lift upward by the projections, 19 a and 19 b, of the top 14 a of the housing 14 to a position shown with the broken lines in FIGS. 4B and 4C.

FIGS. 5A and 5B show the side tab 17 of the cage 12 to cause the downward force to the heat sink 15. This side tab 17 is integrally formed with the cage 12 by cutting several points in the sides of the aperture 12 c with a preset interval and bending cut portions inward so as to form an arched cross section. The side rib 16 of the heat sink 15 in the upper surface thereof abuts against this arched tab 17 to be pressed downward when the cage 12 is free from the transceiver 13. When the transceiver 13 is set within the cage 12, the heat sink 12 is lifted upward withstanding this downward force caused by the arched tab 17 to the upper surface of the side rib 16.

While this invention has been described with reference to illustrative embodiments, this description is not intended to be construed in a limiting sense. Various modifications and combinations of the illustrative embodiments, as well as other embodiments of the invention, will be apparent to persons skilled in the art upon reference to the description. It is therefore intended that the appended claims encompass any such modifications or embodiments. 

1. A mechanism to dissipate heat from a pluggable optical transceiver set in a cage to a heat sink assembled with said cage through a thermo-conducting sheet put between said transceiver and said heat sink, said mechanism comprising: at least a projection provided in a rear end of said optical transceiver; at least a rail with a pocket provided in said heat sink; and a mechanism provided in said cage and said heat sink to cause a downward force to said heat sink, wherein said projection first lifts said heat sink upward withstanding said downward force by running on said rail of said heat sink when said optical transceiver is inserted into said cage, and wherein said projection finally falls within said pocket of said heat sink to adhere said thermo-conducting sheet to said optical transceiver when said optical transceiver is set in a final position within said cage.
 2. The mechanism according to claim 1, wherein said optical transceiver provides two projections apart from each other in a direction along which said optical transceiver is inserted into said cage and without overlapping along said direction, and wherein said heat sink provides two rails each having a pocket, one of said projections first running on one of said rails to lift said heat sink upward and another of said projections subsequent running on another of said rails to level said heat sink.
 3. The mechanism according to claim 2, wherein said two projections each falls within said pocket accompanied with respective rails when said optical transceiver is set in said final position within said cage.
 4. The mechanism according to claim 1, wherein said projection is free from said thermo-conducting sheet in any positions of said optical transceiver with respect to said cage.
 5. The mechanism according to claim 1, wherein said cage provides a window through which said heat sink exposes, wherein said heat sink is movable within said window in vertical while substantially immovable within said window in horizontal.
 6. The mechanism according to claim 5, wherein said mechanism to cause said downward force to said heat sink includes an elastic tab formed in an edge of said window, wherein said elastic tab abuts against a rib provided in said heat sink to cause said down ward force.
 7. The mechanism according to claim 6, wherein said elastic tab has an arched cross section.
 8. A pluggable optical transceiver to be set in a cage with a heat sink to dissipate heat from said optical transceiver through a thermo-conducting sheet, said heat sink being applied with a downward force from said cage when said cage is free from said transceiver and providing a first rail with a first pocket and a second rail with a second pocket, said optical transceiver comprising: a first projection provided in a surface to come in contact with said thermo-conducting sheet; and a second projection provided in said surface, said second projection being not overlapped with said first projection in a direction along which said optical transceiver is inserted into said cage, wherein said first projection of said optical transceiver first runs on said first rail of said heat sink to lift said heat sink upward when said transceiver is inserted into said cage, and wherein said first projection is set within said first pocket and said second projection is set within said second pocket such that said heat sink is adhered to said surface of said transceiver with putting said thermo-conducting sheet therebetween when said transceiver is set in a regular position within said cage.
 9. The pluggable optical transceiver according to claim 8, wherein said thermo-conducting sheet is provided in said heat sink, and wherein said first projection and said second projection are apart from said thermo-conducting sheet.
 10. The pluggable optical transceiver according to claim 8, wherein said first projection and said second projection each provides slopes in respective edges along a direction along which said optical transceiver is inserted into said cage.
 11. A cage assembly for a pluggable optical transceiver, comprising: a cage configured to receive said pluggable optical transceiver, said cage providing an window in a top thereof and an elastic member causing a downward force to said heat sink; and a heat sink adhered with a thermo-conducting sheet, said heat sink exposing from said window and being movable within said window in vertical and substantially immovable in horizontal, said heat sink providing a rail with a pocket in a surface where said thermo-conducting sheet is adhered thereto, wherein said rail is run on with a projection provided in a surface of said transceiver to lift said heat sink upward withstanding said downward force when said optical transceiver is inserted into said cage, and wherein said pocket receives said projection of said optical transceiver to adhere said thermo-conducting sheet to said optical transceiver when said transceiver is set in a regular position within said cage.
 12. The cage assembly according to claim 11, wherein said heat sink has a slope between said rail and said pocket.
 13. The cage assembly according to claim 11, wherein said cage provides an elastic tab in an edge of said window, and said heat sink provides a side rib, wherein said elastic tab abuts against a top surface of said side rib of said heat sink to cause said downward force to said heat sink.
 14. The cage assembly according to claim 13, wherein said elastic tab includes a plurality of tabs each having an arched cross section, each of said tabs being formed by cutting said edge of said window with a preset interval and bending cut portions inward.
 15. The cage assembly according to claim 11, wherein said cage provides a stopper within said window to receive said downward force when said cage is free from said optical transceiver.
 16. The cage assembly according to claim 15, wherein said stopper is formed by bending an edge of said window downward and extending a tip of said bent edge longitudinally so as to receive a bottom corner of said heat sink. 